2.0 Analysis 2.1 General Although the flight crew members were certified and qualified for the flight, they lacked training in specific areas. Similarly, although the aircraft was certified for flight in known icing conditions, inadequate stall warning and low speed warning contributed to the occurrence. This analysis discusses flight crew actions and decision making, the need for more comprehensive flight crew training, and the need for more effective aircraft stall warning and low speed warning. 2.2 Flight Crew Actions and Decision Making When the flight entered cloud during the descent into Timmins and began to pick up light rime ice, which increased to moderate mixed ice, the flight crew was entering a critical, high-workload phase of flight. The aircraft was approximately 2minutes from the initial fix for the approach, and ice was accumulating in unusual areas, such as on the engine nacelles. Despite the ice accumulation, no consideration was given to altering the approach airspeed or aircraft configuration, or the use of autopilot. The crew was aware that the minimum airspeed in sustained icing conditions is 140 KIAS, but did not consider that airspeed restriction applicable during the final approach phase of flight and, therefore, planned to fly the approach at a normal approach speed of 125KIAS. The crew's focus was on the ice accumulating on the airframe and wing leading edges, rather than on monitoring the approach and aircraft performance. As a result, the crew members did not select the autopilot approach mode to On, and the autopilot remained in FMS and altitude-hold mode. Although the ILS frequency was selected, and localizer and glide slope guidance was available, the crew did not notice that the autopilot was not selected to follow that guidance. When the landing gear was lowered just prior to the Sandy Falls NDB, engine power was reduced in anticipation of the aircraft descending on the glide slope. Neither the PF nor the PNF was monitoring the flight instruments, and neither noted that the aircraft remained level at 2700feet asl and the airspeed decreased. A lack of CRM and division of cockpit duties during this high-workload portion of the flight resulted in critical flight parameters not being monitored. Although neither flight crew member characterized the icing conditions as severe, it was noted that ice was accumulating in unusual areas, such as on the engine nacelles. According to the limitations section of the AFM, this is one of several visual cues that indicates severe icing. The AFM also states that use of the autopilot is prohibited when any of the specified visual cues exist. Both pilots, having recently completed surface-contamination and airborne-icing courses, should have been aware of the material in TC Advisory Circular No.0130R, that states in part, it is highly recommended that pilots disengage the autopilot and hand fly the aircraft when operating in icing conditions. In this occurrence, the autopilot functioned as designed; it maintained the selected altitude and trimmed the aircraft to full nose up as the airspeed decreased to 98KIAS. With the autopilot engaged, the increasing angle of attack and nose-up trim were not noticed by the flight crew until it was too late to avoid the stall. Hand flying the aircraft likely would have contributed to the pilots' ability to understand their situation and detect the decreasing airspeed situation early enough to take corrective action. Since the flight crew did not characterize the icing conditions as severe, the decision to fly the approach with autopilot engaged was not contrary to the AFM. In fact, the use of the autopilot was in accordance with company SOPs. 2.3 Flight Crew Training 2.3.1 Flight Simulator Training Training in stall recognition and recovery, often conducted exclusively in the simulator, generally involves initiating recovery at the first indication of stall. The first indication is normally the artificial stall warning, which activates at least five knots above the stall. During this type of stall training, pilots do not see the full stall characteristics of the aircraft, such as any noticeable buffet or wing rock, or a tendency for a wing to drop. With this type of training, pilots may never have an opportunity to practise recovery from a full stall. Although flight crews receive mandatory ground training in airborne icing, the ability to train in a simulator for flight in actual icing conditions is limited. The changes to stall characteristics with ice accumulation typically are not duplicated in training, including the increase in stall speed and the onset of the stall before the activation of the artificial stall warning. Also, it is difficult to account for changes to normal stall symptoms such as buffet or an increased tendency for a wing drop. Without the benefit of having experienced these stall symptoms, pilots can be ill-prepared to recognize contaminated wing stall symptoms. Also, they may not be aware that an ice-induced stall will require a more aggressive recovery technique in which the nose is lowered more aggressively (altitude permitting) to reduce the angle of attack and trade altitude for airspeed. The stall warning horn in C-GEJE did not activate either prior to or during the stall. The flight crew did not notice any buffet or other symptoms of an approaching stall. When the stall occurred, the PF was aggressive in lowering the aircraft's nose to reduce the angle of attack and rapidly gain airspeed. The resulting altitude loss of 850 feet was not uncommon for a recovery from a full stall; however, the altitude loss would have been lessened if the PF had not momentarily released back pressure when the aircraft was in a 30 nose-down attitude. Comprehensive stall training in a controlled environment may help the flight crew to recognize stall symptoms such as buffet. Most advanced simulators can be programmed with available flight test data to simulate aircraft pre-stall and post-stall behaviour. The TSB recognizes that simulator training is expensive and that course designers must balance training exercises with the probability that flight crews may need to employ the techniques learned in the simulator. Simulation of in-flight icing scenarios that have resulted in accidents or serious stall/upset events could help prepare flight crews to deal with actual icing conditions and give them a better understanding of the risks involved with flight in icing conditions. Emphasis on operational changes, such as cycling pneumatic de-ice boots early and often, manually flying the aircraft when in icing conditions, keeping airspeed at or above ice-penetration speeds, and exiting icing conditions as quickly as possible could mitigate stalls in icing conditions. 2.3.2 Crew Resource Management Training Effective CRM is essential to ensure a safe flight operation. Other than the CRM training the crew members received during their aircraft type training at FSI, neither pilot had any recent, formal CRM course. The CRM training provided by FSI was only one of many subjects covered in the ground school portion of the course. This non-exclusive type of CRM training can be a worthwhile refresher, but it does not serve as a substitute for a comprehensive, dedicated CRM course. Although some aspects of CRM may be covered under CARs, PartVII, Standard724.115, Training Programs, a dedicated CRM course is not mandatory. Unless 704operators voluntarily include formal CRM training in their training plans, flight crews will only be incidental to CRM training. The flight crew did not discuss appropriate procedures for conducting the approach in icing conditions, either prior to or during the approach. There was no discussion about aircraft limitations, the use of the autopilot in icing conditions, or the possible visual signs of severe icing. There was ineffective workload management during a heavy workload phase of flight, which resulted in critical flight parameters not being monitored by either crew member. Overall, the flight crew did not employ effective CRM during the approach. 2.3.3 Training in the Duties of Pilot Not Flying The PNF is an integral part of a two-person flight crew with important cockpit duties. Specific training in the role of PNF is important to prepare the PNF to successfully carry out those duties. However, there is no regulatory requirement to provide training in PNF duties, or to evaluate a pilot's performance in the PNF role. The PNF had no opportunity to act as PNF during his initial type training at FSI. This likely contributed to an ineffective division of duties during the approach. Rather than monitoring the primary flight instruments and advising the PF of deviations from the intended airspeed and flight path as soon as they occurred, the PNF likely assumed that the PF was monitoring the primary flight instruments and the autopilot's performance. He then became distracted with other PNF duties such as lowering the landing gear, checking that it was down and locked, and checking the ice accumulation on the airframe and wing leading edges. 2.4 Aircraft Stall Warning The stall warning systems required by CARs, PartV, Airworthiness Standards523.207, are intended to provide flight crews with adequate warning of proximity to a stall. However, when an aircraft is operating in icing conditions in which the stall angle of attack may be markedly reduced, the systems often do not provide adequate warning. In this occurrence, the aircraft stalled without any pre-stall warning and at a higher airspeed than would be expected with an uncontaminated wing. The stall warning system did not provide a warning to the pilots because it was not designed to account for aerodynamic degradation with ice contamination on the wings, or to adjust its warning to compensate for the reduced stall angle of attack. This unsafe condition is not unique to the King Air 350 and exists on numerous other turboprop aircraft. 2.5 Aircraft Low Airspeed Warning This occurrence, and others, indicate that reliance on flight crew vigilance and existing stall warnings is not always sufficient in preventing hazardous low airspeed situations. Furthermore, the onset of flight at unsafe low airspeeds is not unique to flights using an autopilot, or operations in icing conditions. Low airspeed alert systems are designed to alert the flight crew members to the aircraft's decaying airspeed in time for them to take corrective action and avoid the stall. A low airspeed alert, associated with the minimum operationally acceptable airspeed for a particular phase of flight, would help flight crews maintain airspeed awareness in much the same way that altitude alert systems help flight crews maintain altitude awareness. The number of accidents and incidents involving flight crew failure to maintain adequate airspeed would be substantially reduced if low airspeed alert systems were developed and made mandatory. The following TSB Engineering Laboratory report was completed: This report is available from the Transportation Safety Board of Canada upon request. 3.0 Conclusions 3.1 Findings as to Causes and Contributing Factors During the approach, the flight crew did not monitor the airspeed, and it decreased until the aircraft stalled. The aircraft stalled at a higher-than-normal airspeed for the configuration because it had accumulated ice on critical flying surfaces during the approach. The aircraft stall warning system did not activate because it was not designed to account for the aerodynamic degradation from the ice accumulation, or to adjust its warning to compensate for the reduced stall angle of attack caused by the ice. During the approach, the autopilot was not changed from the altitude-hold mode to the approach mode; therefore, the aircraft did not intercept the glide slope. As a result, when the pilot flying decreased the engine power in anticipation of glide slope interception, the aircraft decelerated in level flight. Because the aircraft was on autopilot, the flight crew members did not notice any indications of impending stall, nor did they notice any signs of decreasing airspeed such as increasing nose-up attitude, trim changes, increasing angle of attack, and less responsive controls. The flight crew did not consider that the 140-knot minimum airspeed in sustained icing conditions applied to all phases of flight, including the approach. The crew, therefore, planned to fly the approach at a normal approach airspeed of 125KIAS (knots indicated airspeed). Because the flight crew members did not characterize the icing conditions as severe, they did not follow the precautions specified in the aircraft flight manual for flight in severe icing conditions, such as requesting priority handling from air traffic control to exit the icing conditions, or disengaging the autopilot. The flight crew did not practise effective crew resource management (CRM) during the approach: there was no discussion of appropriate procedures for conducting the approach in icing conditions, and critical flight parameters were not effectively monitored by either crew member. 3.2 Findings as to Risk Other than the CRM training both flight crew members received during their aircraft-type training at Flight Safety International (FSI), neither pilot had any recent, formal CRM training. Since the flight was conducted under Canadian Aviation Regulation (CAR)604, specific CRM training was not required, nor is it required for CAR704 operations. The first officer, who was the pilot not flying (PNF), had no specific training in the role and duties of the PNF during his initial type training at FSI, and there is not a regulatory requirement to receive this type of training. Typically, flight crews receive only limited training in stall recognition and recovery, where recovery is initiated at the first indication of a stall. Such training does not allow pilots to become familiar with natural stall symptoms, such as buffet, or allow for practise in recovering from a full aerodynamic stall. Typically, the training of flight crews for flight in icing conditions is limited to familiarization with anti-icing and de-icing equipment and simulator training, while the opportunity to train for flight in actual icing conditions is limited. Inappropriate guidance on pneumatic de-ice boot operating procedures can lead to de-ice boots being used in a less-than-optimal manner. Inconsistent guidance on autopilot use in icing conditions can lead to its use in conditions where hand flying would provide an increased opportunity to recognize an imminent stall. Typically, aircraft such as the Raytheon B300 are not equipped with a low airspeed alerting system.